Merge tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu into staging

Hi,

"Host Memory Backends" and "Memory devices" queue ("mem"):
- Support and document VM templating with R/O files using a new "rom"
  parameter for memory-backend-file
- Some cleanups and fixes around NVDIMMs and R/O file handling for guest
  RAM
- Optimize ioeventfd updates by skipping address spaces that are not
  applicable

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# gpg:                using RSA key 1BD9CAAD735C4C3A460DFCCA4DDE10F700FF835A
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# gpg: Good signature from "David Hildenbrand <david@redhat.com>" [unknown]
# gpg:                 aka "David Hildenbrand <davidhildenbrand@gmail.com>" [full]
# gpg:                 aka "David Hildenbrand <hildenbr@in.tum.de>" [unknown]
# gpg: WARNING: The key's User ID is not certified with a trusted signature!
# gpg:          There is no indication that the signature belongs to the owner.
# Primary key fingerprint: 1BD9 CAAD 735C 4C3A 460D  FCCA 4DDE 10F7 00FF 835A

* tag 'mem-2023-09-19' of https://github.com/davidhildenbrand/qemu

:
  memory: avoid updating ioeventfds for some address_space
  machine: Improve error message when using default RAM backend id
  softmmu/physmem: Hint that "readonly=on,rom=off" exists when opening file R/W for private mapping fails
  docs: Start documenting VM templating
  docs: Don't mention "-mem-path" in multi-process.rst
  softmmu/physmem: Never return directories from file_ram_open()
  softmmu/physmem: Fail creation of new files in file_ram_open() with readonly=true
  softmmu/physmem: Bail out early in ram_block_discard_range() with readonly files
  softmmu/physmem: Remap with proper protection in qemu_ram_remap()
  backends/hostmem-file: Add "rom" property to support VM templating with R/O files
  softmmu/physmem: Distinguish between file access mode and mmap protection
  nvdimm: Reject writing label data to ROM instead of crashing QEMU

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>